Adjusting and calibrating of pressure switches

ABSTRACT

The force or degree of compression of the spring is adjusted by rocking the lever about its axis A-B by means of the manually operated cam acting on the lever at D. Calibration is effected by adjusting the screw at B to rock the lever about axis A-D. Any tool forces applied to the adjusting screw during adjustment cannot be transmitted to the spring to adversely affect calibration.

United States Patent [72] Inventor Erich Kothe Schiller Park, Ill. [21}Appl. No. 881,207 [22] Filed Dec. 1, I969 [45] Patented Dec. 21, 1971[73] Assignee Controls Company 01 America Melrose Park, Ill.

[54] ADJUSTING AND CALIBRATING 0F PRESSURE SWITCHES 5 Claims, 4 DrawingFigs.

U.S. Cl 267/158 F161 1/18 Field of Search 267/ 158, 159, 160, 150

[56] References Cited UNITED STATES PATENTS 2,511,526 6/1950 Bugge267/159 3,185,141 5/1965 Mirackietal Primary Examiner-James B. MarbertAttorneys-John W. Michael, Gerrit D. Foster, Bayard l-l.

Michael, Paul R. Puerner, Joseph A. Gemignani, Andrew 0. Riteris,DanielVan Dyke and Spencer B. Michael ABSTRACT: The force or degree ofcompression of the spring is adjusted by rocking the lever about itsaxis A-B by means of the manually operated cam acting on the lever at D.Calibration is effected by adjusting the screw at B to rock the leverabout axis A-D. Any tool forces applied to the adjusting screw duringadjustment cannot be transmitted to the spring to adversely affectcalibration.

PATENTEDnEnmsn 3 52 7 W g/W dfw'rzgy ADJUSTING AND CALIBRATING OFPRESSURE SWITCHES BACKGROUND OF INVENTION Pressure switches have beenprovided with cam-actuated levers for adjusting the spring force of thepressure switch and, thus, the level to be sensed by the switch. Sincethe nature of the device requires calibration after assembly, the leverwas provided with a calibrating screw. Tool forces applied to thecalibrating screw could be transmitted to the spring and affect thecalibration. This could result in improper calibration or prolong thecalibration process.

SUMMARY OF INVENTION The present construction provides a lever which canbe adjusted about an axis defined by a fixed pivot point A and a pivotpoint B which is also an adjusting screw. The lever is in the generalform of a plate with the cam acting at a point D remote from theadjusting axis. The lever acts on the spring at a fourth point C remotefrom the other points. When the ad justing screw at B is moved, thelever rocks about axis A-D and moves point C to calibrate the spring.Tool forces applied to the screw during calibration cannot influence thespring. Therefore, the calibration process is more accurate and faster.

DESCRIPTION OF DRAWINGS FIG. 1 is a top plan view of the apparatus.

FIG. 2 is an elevation taken from the right in FIG. 1.

FIG. 3 is a partial elevation taken from the right in FIG. 2.

FIG. 4 is a perspective with some parts broken away for clarity.

DESCRIPTION OF PREFERRED EMBODIMENT The details of the pressure switchare not shown here. It is only important to know that the compression ofthe spring is to be adjusted in use and the unit should be calibrated atthe factory so the actual compression of the spring corresponds to theindications associated with the manual adjusting arrangement. The spring10 is housed in a plunger 12 which lies under one comer C of thegenerally rectangular level 14. The lever is pivoted at A in the fixedbracket 16 while another comer B is provided with a finger 18 which isformed and notched at 20 to fit over and be guided by the adjacentbracket portion 22 which carries the calibrating screw 24 against whichthe finger l8 bears by reason of the bias of spring 10. This point canbe called B. The fourth comer of the lever is formed to provide afollower 26 bearing at D against the cam 28 pivoted at 30 in the bracketand actuated by arm 32. The spring force tries to push lever 14 up at Cwhich pushes down at A and up at B and D. The lever is held againstcalibrating screw 24 and Cam 28 by the spring.

When the arm 32 is moved, it rotates the cam 28 about its pivot 30 toraise or lower lever 14 at D. Since A and B are fixed, the lever 14rocks about the axis determined by A-B to adjust C and the spring 10. Ifthe calibrating screw 24 is adjusted, point B is raised or lowered andthe lever 14 must rock about axis A-D to thereby adjust C and spring 10.Since the screw is supported by the bracket, any tool forces applied tothe screw cannot influence the force of spring 10. Calibration of thespring is, therefore, isolated from undesired influences.

An advantage of this design is that an extra low setting of the springcan be achieved by allowing the lever to strike an adjustable stop whichcan be accurately calibrated for the specified value.

Since calibration tool forces cannot affect the spring force beingcalibrated, this design lends itself to advanced or automatedcalibration techniques.

For simplicity, A-B and C-D are generally parallel. This avoids motionmultiplying effects having to be considered in designing the cam.

I claim:

1. Apparatus for adjusting and calibrating a spring comprism 1 bracket,

a lever mounted on the bracket for pivoting about an axis A-B wherepoint A is a fixed pivot, and point B is an adjustable calibrating screwspaced from A, a compressed spring to be adjustably loaded and actedupon by said lever at a point C spaced from A and B and not on the A-Baxis, an adjusting device acting on the lever at a point D spaced fromA, B and C and not on the A-B or A-C axis whereby movement imparted tothe lever at D by the device pivots the lever about the A-B axis andcauses movement at C to adjust the compression of the spring; adjustmentof the calibrating screw B being effective to pivot the lever about theA-D axis and cause movement at C to adjust the compression of thespring.

2. Apparatus according to claim 1 in which A-B and C-D are generallyparallel.

3. Apparatus according to claim 1 in which the calibrating screw iscarried by the bracket and acts on the lever while the compressed springurges the lever against the screw.

4. Apparatus according to claim 3 in which the lever is urged againstthe adjusting device by the spring.

5. Apparatus according to claim 4 in which the adjusting device is a campivoted on the bracket.

1. Apparatus for adjusting and calibrating a spring comprising: abracket, a lever mounted on the bracket for pivoting about an axis A-Bwhere point A is a fixed pivot, and point B is an adjustable calibratingscrew spaced from A, a compressed spring to be adjustably loaded andacted upon by said lever at a point C spaced from A and B and not on theA-B axis, an adjusting device acting on the lever at a point D spacedfrom A, B and C and not on the A-B or A-C axis whereby movement impartedto the lever at D by the device pivots the lever about the A-B axis andcauses movement at C to adjust the compression of the spring; adjustmentof the calibrating screw B being effective to pivot the lever about theA-D axis and cause movement at C to adjust the compression of thespring.
 2. Apparatus according to claim 1 in which A-B and C-D aregenerally parallel.
 3. Apparatus according to claim 1 in which thecalibrating screw is carried by the bracket and acts on the lever whilethe compressed spring urges the lever against the screw.
 4. Apparatusaccording to claim 3 in which the lever is urged against the adjustingdevice by the spring.
 5. Apparatus according to claim 4 in which theadjusting device is a cam pivoted on the bracket.